RE: Question on DS-TE (solution) draft: How can I prevent preemption of a connection ?

["Choudhury, Sanjaya" <Sanjaya.Choudhury@marconi.com>]

Hi Francois!

> -----Original Message-----
> From: Francois Le Faucheur [mailto:flefauch@europe.cisco.com]
> Sent: Wednesday, December 12, 2001 1:47 PM
> To: Choudhury, Sanjaya
> Cc: 'te-wg@ops.ietf.org'
> Subject: Re: Question on DS-TE (solution) draft: How can I prevent
> preemption of a connection ?
> 
> 
> Sanjay,
> 
> At 09:54 12/12/2001 -0500, Choudhury, Sanjaya wrote:
> 
> >         Hi! According to the latest DS-TE solution, the 
> signaled (setup)
> >         preemption priority is used to infer the bandwidth 
> constraint
> >         associated with a LSP.
> >
> >         By doing this, are we losing the ability to prevent 
> the preemption
> >         of a LSP (of a set of LSPs) , in a network using the DS-TE ?
> >
> >         [For example, an administrator may want to deploy 
> DS-TE in his
> >         network, but may not want (automatic) preemption of existing
> >         LSPs in response to the creation a new LSP.]
> >
> >         Thanks,
> >         sanjay
> >
> 
> I think you've raised a very valid point:
> As currently specified, the solution would not allow LSPs in 
> different CTs 
> to use the same preemption level.
> 
> I believe this can be fixed by making the solution a little 
> more flexible. 
> In essence what we would do is :
>          - consider that the 8 Bw values included in the IGP 
> advertisments 
> are no longer tied to preemption. The position of the Bw 
> value in the IGP 
> advertisement is considered purely as an index i,  0<=i<=7
>          - a mapping is defined on all the LSRs: i ---> 
> (preemption_level, CT)
>          - this mapping must be consistent throughout the DSTE domain
> 
> For example, I could use the above to ensure each CT has a differnet 
> preemption level (ie CT0 can preempt CT1, CT1 can preempt CT2) by 
> configuring the following mapping:
>          - BW value 0 is used for CT0/Preemption0
>          - BW value 1 is used for CT1/Preemption1
>          - BW value 2 is used for CT2/Preemption2
> 
> Alternatively, I could use the above to ensure all CTs have the same 
> preemption level by configuring the following mapping:
>          - BW value 0 is used for CT0/Preemption0
>          - BW value 1 is used for CT1/Preemption0
>          - BW value 2 is used for CT2/Preemption0
> 
> I had a chat with some of the co-authors about this and they 
> were fine with it.
> 
> Does that work for you too?
> 
> Thanks
> 
> Francois
> 
> >
> >
> >

	Can you explain the solution again ?
	
	IGP: 
		1. 8 available bw are advertised, using existing 
		constructs. ->Okay
		2. How do I compute these ? 
			a) Based on setup priority
			b) Based on setup priority + class type (/BC)
			c) Based on class type(/BC)
	CAC:
		1. How do I get the BW pool with which I need
		to compare the requested BW with ?
			a) From the setup priority ?
			b) New signaled TLV ?
			c) Combination of both ?
	PCM:
		1. When I need to compute a PATH for a connection
		what approach do I use ?
		[Related to CAC]

	Preemption:
		1. How do I determine which connection to preempt ?
			a) Based on the standard setup/holding 
			priority ?
			b) Based on a new signalled entity ?
			c) combination of both ?
		2. How can I say don't preempt a specific connection ?

	Thanks,
	sanjay
		
> 
>